Process of preparing alkanolamines



Dec. 16, 1952 P. FERRERO vE'ru. 2,622,073

PROCESS oF PREPARING ALKANOLAMINES Filed June 26, 1947 PA UL FER ERO, FRANCO/5 BERRE and L 0^/ REN FLA/MME Patented Dec. 16,A 1952 Y*UNIT-ED STATES PATENT OFFICE `Paul Ferrero, Tertre, and Franois Berb andfLon Ren Flamme, -;St. Ghislain, ,-Belgium, -assignors .to Societe Carbochimique, Societe Anonyme, `.Brussels, Belgium, a company .of Belgium Applicationlunef, 1947, Serial'No. `757;318 IniBe'lgium Marchl, 19.4.7

secondary and tertiary famines,fmay only -betcarried out'by using a considerable cex'cessof fam- ,monia in `relation to Vthe .olefine oxide, which vexcess may rbe as .-much :as 50 molesof ammoni-a'to .1 .mole of oxide. The reaction carried out under these conditions at atmospheric pressure, Vwith `ammoniacal :solutions of :a 'density ybetween, lfor example, 0.9.1 Yand ,0.93 .at 115 C'., leads :t0 rsuch .dilutions of the aminesiin the :Final solution that certain producers haveghad to'resortto :special means for reducing the calorific expenditure necessary for obtaining .amines in the anhydrous state.

It 'is also `known .that the .duantityf primary amines `obtained for a given excess of ammonia mayfto a certain extent, beinereased by voperating in the presence of .volatilemineral acidsleading to amine .salts which must -thenbe decomposed. On the other hand, .the employment of slight ammoniacal excesses leads, vas is known, to the formation of `tertiaryamines in the presence of small quantities of .primary and secondary amines. Aeertai-n excess `of alkali is actually essential if it is desired to avoid the formation of by-products by reaction .of olei'ineuoxide -,on the tertiary amines.

In the presence of an excess of ammonia Vbetween that directing .,the -reaction towards vthe monoalkanolamines Vandthat directing it `towards the tri-alkanolamines, `there kis obtained, with acceptable Yconcentrations sof `between 100 to 200 grams per litre, a mixture Aof vamines in which`the proportion of di-alkanolamines lbecomes Iconsid erable.

The reaction :of .ethylene oxide :on ammonia for example develops according to v-the following mechanism:

We have established `that r`the yperoentage ,at equilibriumpf `the three amines: mono.,,di `and tri-ethanola-mine, is la Vfunction of the `ammonia oxide `molecular ratio being employed; thel curves fof Figure l of `the accompanying drawing reprersent these .results expressed in :mole percent 'at' a 'temperature of ,15 C.

For .an ,ammonia/oxide molecular ratio `of 5: for example, there is obtained, with a -concentration of about`=1v1% tan ami-ne Lmixture having fa rmola-r ycomposition v'of 5.7% mono 28% di- Aand 1.5% tri-.ethanclamina or, vby weight, 40% Vmono, .3,41% :diand 26% tri-ethanolamine.

.Off the threeamines under consideration, the greatest :demand is forthefmonoand 'the triiethanolam-ine; consequently, rit is interesting `to A-try to reduce, and even ,tosuppress the lformation of cli-ethanolamineor, morebroadlmrthe'secyondary gamine, --and it is this' which -is v.the :object of the :present invention.

iBy referring to the law :of :mass action, it may be accepted vas va `vpriori that fthe `addition of di- -ethanolamine to Vthe ammomia/exide reaction .mixture wou,lidi-lead to a reduction of the :amount of `.secondary amine vformed. and that :one would .succeed in completely'suppressing 4its Yformation -by J'adding -a predetermined :quantity vof -di-ethanolamine, equal Eto -that which is *normally formed .at the -equilibrium Afor xed conditions vof excess .-of ammonia, say, .-10.14 .mole di-ethanolamine for-an NH3/oxide molecular ratio of Y3:1,

0.17 -mole -diethanolamine for a F511 v ratio :and 07.16 mole di-ethanolamine ifor 1a I10:51 ratio; vthe vquantities :being given per fmoleo'f 4voxide used, fas is ;clearly-;shown in Figure r2 Ltcurve lr) "of tthe racfcompanying -Ldrawi-ng. 'Now our investigations have shown that the addition of such quantities of di-ethanolamine does .no t'produce the anticipated result; actually, there remain respectively 8,;9 land I7 gms. of di-ethanolamine per -100 gms. of :amines yformed under the operational conditions referred lto above. Similar `findings Aare obtained when using propylene oxide or'higher olefine oxides.

According tothe jpresent invention, in order to reduce -or suppress the production of secondary amine, lthere is added'to the-reactants fbeing used, a quantity of this amine which is greater than the quantity which is fcrmedat equilibrium under the conditions which have been considered.

We have actually found that', 'in order `to 'suppress, for example, ranyiorrlnation of di-ethanollspendi-ng Afto equilibrium, ibut surprisingly 5to the quantity of mono-ethanolamine which is formed at equilibrium. Thus, it is only by using respectively 0.18, 0.23 and 0.33 mole di-ethanolamine for theHNHs/oxide ratios ofv3:1,l5:1 and 10:1 (curved of Figure 2)', that all the oxide introduced is converted only into monoand triethanolamine, the added secondary amine being recovered at the end of the operation.

Contrary to what may be assumed, the curves of Figure 2 show that, as a function of the molecular ratio of ammonia/ethylene oxide that is employed, the quantity of di-ethanolamine necessary to suppress its formation (curve d) increases continuously, lalthough the quantity of di-ethanolamine which is formed at equilibrium (curve b) commences by increasing, lpasses through a maximum and finally regularly decreases. By using quantities of di-ethanolamine les-s than those hereinbefore mentioned, the oxide is converted int-o ya mixture of three amines, the proportion of secondary amine being yless than thatat the equilibrium shown in Figure 1.

By' using quantities of di-ethanolamine greater than those hereinbefore mentioned, the oxide is similarly converted into only `monoand triethanolamine; moreover, in this case, a part of the added di-ethanolamine is also converted into triethanolamine.

Thus, for example, starting with ethylene oxide and ammonia in aqueous solution, the present in- -vention provides ya process for the preparation of a mixture of the three corresponding amines and a process in which the quantity of d-iethanolamine formed is reduced as desired, or even suppressed, by adding beforehand the requisite quantity of -diethanolamine tothe reactants being used, such quantity being proportional to that of the m'ono-ethanolamine which is formed under the conditions that have been considered.

We have shown experimentally thatthe factor of proportionality between the mean concentration of di-ethanolamine which it is necessary to have present, by prior addition of this amine, in order to suppress its formation, and the mean concentration of mono-ethanolamine, is the ratio of the constants of the speed of reaction of ethylene oxide on mono-ethanolamine on the one hand, yand on di-ethanolamine on the other hand.

Another Way of vcarrying out the present invention consists in initially adding an excess o-f di-ethanolamine as compared with the quantity which corresponds to the suppression of its formation so as to convert this excess 'into tri- -ethanolamine, the nal mixture of amines which is formed comprising only the monoand the triethanolamine.

Example 1 Example 2 VOn the one hand, 44 parts of ethylene oxide and, on the other hand, 390 parts of ammoniacal solution having a, density of 0.92 to which are added 24 parts of di-ethanolamine, are continuously introduced, per hour, into the reaction apparatus maintained at 15 C.

The product of the reaction is continuously drawn off. vAfter eliminating the excess ammonia and the Water, the composition of ethanolamines formed, when the di-ethanol-amine used is abstracted, is 40 parts mono-ethanolamine per 60 parts tri-ethanolamine.

Example 3l On the one hand, 44 parts of ethylene oxide and, on the other hand, '780 parts of -ammoniacal solution having a, density of 0.92 to which are added 35 parts of di-ethanolamine, a-re continuously introduced, per hour, into the reaction apparatus maintained at 15 C. The product of the reaction is continuously drawn olf. After elimination of the excess ammonia and the Water, the composition of ethanolamines formed, when the diethanolamine used is abstracted, is 50 parts monoethanolamine per 50 parts tri-ethanolamine.

Example 4 OnY the one hand, 44 parts of ethylene oxide and, on the other hand, 390 parts of ammoniacal solution of density 0.92 to which is added 30 parts di-ethanolamine, are continuously intro- On the one hand, 44 parts of ethylene oxide and, on the other hand, 390 parts of ammoniacal solution having a density of 0.92, to which are added 20 parts di-ethanolamine, are continuously introduced, per hour, into the reaction apparatus mamtamed at 15 C. The product of the reacf tion iscontinuously drawn olf. After eliminating the excess ammonia and the water, the composition of ethanolamines formed, when the diethanolamine used is abstracted, is of 40 parts mono, 6 parts diand 54 parts tri-ethanolamine.

These examples clearly illustrate the advantages of the process in accordance with the present invention.

The process according to this invention offers a remarkable flexibility in working: in effect, it makes possible the preparation of ethanolamines:

(1) Without formation of di-ethanolamine, with the production of variable proportions of monoand tri-ethanolamine as a function of the molecular ratio of ammonia/oxide that is used: with a ratio 3:l:30% monoand '70% tri-ethanolamine; 5:1:40% monoand 60% tri-ethanolamine; 10:1:50% monoand 50% tri-ethanolamine; 15:1:65% monoand 35% tri-ethanolamine.

(2) With a consumption of di-ethanolamine, by adding a quantity of di-ethanolamine in excess as compared with that which suppresses its formation, this excess being converted during the carrying out of the process into Itri-ethanolamine.

(3) With a formation of di-ethanolamne, by

determining the quantity of di-ethanolamine to be added as a function of the quantity of this amine which it is desired to produce.

It is a remarkable fact that the quantity of mono-ethanolamine formed always remains that which corresponds to equilibrium as a function of the molar ratio of ammonia/oxide, whether Working with or without additions beforehand of di-ethanolamine.

These advantages are associated with a particularly simple process, since it is operated in aqueous solution at normal pressure, without making use of outside reactions whilst obtaining directly acceptable concentrations of amines.

Obviously, the invention is not limited to the foregoing examples: it is applicable whatever may be the molar ratio of ammonia/oxide and the concentration of the ammonia in the solution, and whether operated at the temperature indicated or at lower or higher temperatures, at atmospheric pressure or at greater pressures, in a continuous or discontinuous process.

The various embodiments described with reference Ito the foregoing examples are likewise applicable, within the scope of the invention, to the use of propylene oxide or higher olene oxides with a View to reducing or suppressing the formation of the secondary amine. By higher olene oxides are to be understood, in the present specification, the oxides of olenes capable of reacting with ammonia.

We claim:

1. In the production of alkanolamines .by the reaction of a low molecular alkylene oxide and aqueous ammonia in any specific molar ratio and under any specific reaction condition, wherein the proportions of mono, di, and tri-alkanolamines produced are dependent upon the molar ratios of the reactants and the reaction conditions used, the improvement which cornprises reacting ythe low molecular alkylene oxide and the aqueous ammonia in the presence of an addition of a quantity of the di-alkanolamine produced by said reaction in excess of the molar amount which would be produced by reaction between said reactants under said specific molar ratio and reaction conditions when no such addition is made.

2. In the production of alkanolamines by the reaction of a low molecular alkylene oxide and aqueous ammonia in a molar ratio of ammonia to alkylene oxide varying between 3:1 and 20:1 and under any specific reaction condition, wherein mono, di, and tri-alkanolamines are normally produced in proportions dependent upon the molar ratios of the reactants and the reaction conditions used, the improvement which comprises reacting the low molecular alkylene oxide and the aqueous ammonia in the presence of an addition of a quantity of the di-alkanolamine produced by said reaction in excess of the molar amount which would be produced by reaction between said reactants under said specic molar ratio and reaction conditions when no such addition is made which causes the formation of substantially only mono-alkanolamine and tri-alkanolamine under said specific molar ratio and reaction conditions.

3. In the production of ethanolamine by the reaction of ethylene oxide and aqueous ammonia in any specific molar ratio and under any speciic reaction condition, wherein the proportions of mono, di, and tri-ethanolamines produced are dependent upon the molar ratios of the reactants and the reaction conditions used, the improvement which comprises reacting ethylene oxide and the aqueous ammonia in the presence of an addition of a quantity of di-ethanolamine in excess of the molar amount which would be produced by reaction between said reactants under said specific molar ratio and reaction conditions when no such addition is made.

4. In the production of ethanolamines by the reaction of ethylene oxide and aqueous ammonia in a molar ratio of ammonia to ethylene oxide varying between 3:1 and 20:1 and under any specific reaction condition, wherein mono, di, and tri-ethanolamines are normally produced in proportions dependent upon the molar ratios of the reactants and the reaction conditions used, the improvement which comprises reacting ethylene oxide and the aqueous ammonia in the presence of an addition of a quantity of di-ethanolamine in excess of the molar amount which would be produced by reaction between said reactants under said specic molar ratio and reaction conditions when no such addition is made which causes the formation of substantially only monoethanolamine and tri-ethanolamine under said specic molar ratio and reaction conditions.

5. In the production of ethanolamines by the reaction of ethylene oxide and ammonia in varying molar ratios in aqueous solution as represented by Figure 2 of the appended drawing, the improvement which comprises adding to said reactants diethanolamine in excess of a molar amount represented by curve b in said figure.

6. In the production of ethanolamine by the reaction of ethylene oxide and ammonia in varying molar ratios in an aqueous solution as represented by Figure 2 of the appended drawing, the improvement which comprises adding to said reactants diethanolamine in an amount at least approximately equaling the molar amount represented by curve d in said figure.

PAUL FERRERO. FRANCOIS BERB.

LE'oN REN FLAMME.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date Re. 19,632 Arnold July 9, 1935 1,904,013 Reid Apr. 18, 1933 1,988,225 Wickert Jan. 15, 1935 2,051,486 Kautter Apr. 18, 1936 2,085,785 Bottoms July 6, 1937 2,092,431 Swallen et al Sept. 7, 1937 2,373,199 Schwolgler et al. Apr. 10, 1945 FOREIGN PATENTS Number Country Date 497,093 Great Britain Dec. 13, 1938 OTHER REFERENCES G. D. Parkes et al.: Mellors Modern Inorganic Chemistry, (Longmans, Green and Co., 1946). PD. 213-217.

W. F. Ehret: Smiths College Chemistry, (D. pleton Century Co., 6th ed., 1946) Pp. 232 and 

1. IN THE PRODUCTION OF ALKANOLAMINES BY THE REACTION OF A LOW MOLECULAR ALKYLENE OXIDE AND AQUEOUS AMMONIA IN ANY SPECIFIC MOLAR RATIO AND UNDER ANY SPECIFIC REACTION CONDITION, WHEREIN THE PROPORTIONS OF MONO-, DI-, AND TRI-ALKANOLAMINES PRODUCED ARE DEPENDENT UPON THE MOLAR RATIOS OF TH REACTANTS AND THE REACTION CONDITIONS USED, THE IMPROVEMENT WHICH COMPRISES REACTING THE LOW MOLECULAR ALKYLENE OXIDE AND THE AQUEOUS AMMONIA IN THE PRESENCE OF AN ADDITION OF A QUANTITY OF THE DI-ALKANOLAMINE PRODUCED BY SAID REACTION IN EXCESS OF THE MOLAR AMOUNT WHICH WOULD BE PRODUCED BY REACTION BE TWEEN SAID REACTANTS UNDER SAID SPECIFIC MOLAR RATIO AND REACTION CONDITIONS WHEN NO SUCH ADDITION IS MADE. 